Regarding the functions of a system, technical developments have been shifting from unidirectional to bidirectional in recent years. Such shifting indicates that achievement of functions that take differences among individuals into account will become the key technology in the future, and various research communities propose systems in which the psychological state of an individual is inferred by any available method and devices are controlled thereafter using the result of inference. As means for inferring the psychological state of an individual, making inference on the basis of biological information of an individual is deemed as the most reliable means, and studies in this field has been actively conducted in recent years.
Generally, a technique of inferring a comfortable feeling of the user by analyzing the brain wave is known extensively. This technique can be said as useful means in a case where evaluation tests or the like are the purpose. However, because this technique requires large-scale equipment and has a requisite to limit movements of an individual, developing this technique actually at home has been thought as infeasible. It can be said also from the foregoing that a point that has to be considered always when acquiring biological information is how easily biological information is acquired without making the user feel uncomfortable to the extent possible.
When considerations are given to this point, in comparison with the collection of the bran wave for which efforts are currently being undertaken, collecting the pulse wave that is said to have the least possibility of making an individual feel uncomfortable is thought as the most effective means. Regarding the pulse wave, there has been revealed a phenomenon in the first place that a blood flow discharged from the heart and delivered to peripheral fingertips comes under a significant influence of physiological conditions, such as a change in property of a heart rate, hemodynamics, and an arteriolovenular system, and such a change is reflected on the waveform of the pulse wave. Accordingly, in the field of health analysis, a currently proposed technique is to collect the pulse wave of the peripheral blood vessel in the fingertips and infer the health condition from the accelerated pulse wave (for example, see Patent Document 1).
FIG. 60 is a view showing the waveform of the accelerated pulse wave described in Patent Document 1. As is shown in FIG. 60, the accelerated pulse wave is made up of five elementary waves denoted as E1, E2, E3, E4, and E5. Because the peak A of the elementary wave E1 coincides with the start of the diastolic wave in the fingertip plethysmogram, a required time from the peak A to the peak E coincides with the systolic time axial length. The elementary wave E1 is a positive wave that is convex upward with respect to the base line, the elementary wave E2 is a negative wave that is convex downward with respect to the base line, and the following elementary waves E3, E4, and E5 are changeable elementary waves that become either a positive wave or a negative wave depending on the physiological conditions, all of which have a strong correlation with the age of the user.
When the pulse wave of the user is measured, the heart rate increases when the user is in a state of tension and the fingertip blood flow tends to decrease. This gives rise to an influence that a distance b to the peak B from the base line decreases whereas a distance d to the peak D from the base line increases. Hence, in the waveform analysis of the accelerated pulse wave, the health condition is determined by a rate of change in the ratio of the distance b to the distance a (b/a) or in the ratio of the distance d to the distance a (d/a).
Also, with the purpose of enabling the user to maintain satisfactory psychological state and feeling, Patent Document 2 proposes a warm air heating device configured in such a manner that an amount of heat generation by heating means or an amount of air flow by air blowing means becomes irregular with time to enable the user to maintain a warm feeling by maintaining an influence on the automatic nerve for a state of relaxation to be enhanced.
FIG. 61 is a block diagram showing the configuration of the warm air heating device described in Patent Document 2. An air blowing portion 1001 shown in FIG. 61 is formed of a fan motor and a heating portion 1002 is formed of a heat source, such as heating oil or a heater. A temperature sensor 1003 to detect the temperature is provided in the vicinity of the heating portion 1002, and detected temperature information is transmitted to a control portion 1004. The control portion 1004 controls an amount of air blow by the air blowing portion 1001 and an amount of heat generation by the heating portion 1002 by outputting an irregular signal generated by an irregular signal generating portion 1005 to the air blowing portion 1001 and the heating portion 1002 at appropriate timing determined according to a timer signal from a timer 1006 and a detected temperature signal from the temperature sensor 1003.
Also, in order to control the residential environment of the user, an environmental control device has been controlled by detecting environment physical quantities, such as a residential environment temperature (hereinafter, referred to as room temperature), a residential environment humidity (hereinafter, referred to as humidity), a residential environment outside air temperature (hereinafter, referred to as outside air temperature), and an amount of solar radiation. Besides the control based on the environment physical quantities as described above, there has been proposed a technique for inferring a state of the user, such as a state of tension, a state of relaxation, and a state of excitation through chaos analysis of biological information of the user to control the environment control device on the basis of the result of inference.
For example, Patent Document 3 proposes a multimedia equipment control device configured to control multimedia equipment by inferring a feeling of tension, a feeling of relaxation, and a feeling of excitement of the user from evaluation made by detecting the skin temperature of fingertips or the like of the user (subject) and evaluating the detected skin temperature through chaos analysis or the like.
Also, Patent Document 4 proposes an environment control device configured to control environment conditions by inferring a psychological state or a physiological state of the user through chaos analysis of time-series data of motions of the user (individual).
Also, Patent Document 5 proposes an electronic device that changes a response from a game machine, such as a pinball game machine, by inferring a state of being bored, a state of excitement, and a state of concentration or distraction of the user with respect to the game machine using the Lyapunov exponent obtained through chaos analysis of the pulse wave, a heart rate, or the like collected from the user (player) of the game machine.
Also, Patent Document 6 proposes a bath device provided with a pulse wave detector on the surface of the bathroom remote controller to detect pulse wave data when the user (an individual taking a bath) puts his fingertip on the detector, so that when pulse wave data different from the normal data is detected, the bath device alerts the user to take a rest, informs the family members of such a detection or performs the control to lower the hot water temperature.
Also, Patent Document 7 proposes a technique for enhancing efficiency of job or study of an individual by performing air-conditioning in response to a change of a physiological amount of the sympathetic nerve system by utilizing a phenomenon that when an individual doing a job or studying in a room is getting irritated because of low efficiency, his automatic nerve, in particular, his sympathetic nerve, increases its activity, which causes the skin temperature to drop as the blood flows to the head by an increase of an amount of sweat or the number of pulses, which are the physiological amount of the sympathetic nerve system.
Also, Patent Document 8 proposes a technique of inferring a psychological state of an individual, chiefly a warm feeling, from the amplitude of the pulse wave of an individual, which is determined as having the least possibility of making an individual feel uncomfortable, because a point that has to be considered always when acquiring biological information is how simply the technique is implemented as a system and how least the user is made feel uncomfortable when biological information is acquired.
With the configuration described in Patent Document 1, the health analysis of the user is made with the use of the pulse wave. However, because a comfortable feeling of the user is not inferred, there is a problem that it is impossible to control a stimulus outputted to the user for the user to maintain a comfortable feeling.
Also, with the configuration described in Patent Document 2, the user is enabled to maintain a satisfactory feeling by providing irregularities to the control on the device side. However, because a comfortable feeling of the user is not inferred, this configuration is susceptible to further improvement for enabling the user to maintain a comfortable feeling in a more reliable manner.
Further, although a state of the user is inferred through chaos analysis in Patent Documents 3 through 5, time-series data of biological information over a sufficiently long period, for example, from a few minutes to about 15 minutes, is necessary to infer a state of the user through chaos analysis. This raises a problem that a state of the user cannot be inferred precisely until the sufficiently long period has passed since the acquisition of biological information was started, which makes it impossible to give a suitable stimulus to the user during such a period. In particular, in a case where chaos analysis is adopted to control a device forming the residential environment of the user, for example, an air conditioning device, a lighting device, a video device, or an audio device, it is anticipated that there is a case where time-series data over a sufficiently long period cannot be acquired. Hence, there is a problem that how accurately a state of the user can be inferred during such a period.
Also, there have been proposed various methods and devices for inferring a state of the user through chaos analysis of biological information of the user as in Patent Documents 3 through 6. However, which state of the user can be inferred through chaos analysis of which biological information is still under study and development. In addition, Patent Document 3 describes that a state of tension, a state of relaxation, and a state of excitement of the user can be inferred through chaos analysis of the skin temperature of the user. However, it fails to disclose a correlation between chaos analysis and a comfortable feeling or a thermal sensation in response to a warm or cool thermal stimulus.
In addition, Patent Document 4 describes that it is possible to control an air conditioner or the like by finding a comfortable feeling in response warm or cool thermal through chaos analysis of motions of the user. However, it fails to disclose a correlation between chaos analysis of biological information other than motions of the user and a degree of comfort in response to warm or cool thermal.
Also, Patent Document 5 describes that a state of being bored, a state of excitement, and a state of concentration or distraction of the user can be inferred through chaos analysis of the pulse wave, a heart rate, and the like of the user. However, it fails to disclose a concrete correlation between the Lyapunov exponent obtained through chaos analysis and a state of the user. It also describes that a response to air conditioning can be changed, too. However, it also fails to disclose a correlation between chaos analysis and a comfortable feeling or a thermal sensation in response to a warm or cool thermal stimulus.
Also, Patent Document 6 describes that the device performs the control to lower the hot water temperature upon detection of pulse wave data different from normal data. However, this is to control the hot water temperature by inferring an abnormality of the user from the pulse wave, and not to control the hot water temperature by inferring a comfortable feeling or a thermal sensation of the user in response to a warm or cool thermal stimulus.
Also, in Patent Document 7, plural physiological amounts of the automatic nerve system are collected as biological information used to infer a psychological state of the user. In this case, however, because plural physiological amounts are measured at one time, plural sensors have to be incorporated into the system, which makes it difficult to put this configuration into practical use. In addition, it describes that a psychological state of an individual is inferred by comprehensively determining the measurement results of these plural physiological amounts of the automatic nerve system. However, it fails to disclose clearly a concrete method for making a comprehensive determination.
Also, Patent Document 8 proposes to use the amplitude characteristic of the pulse wave in response to a warm feeling of an individual for the technique of inferring a warm feeling of an individual using the pulse wave, which is one kind of biological information. However, by taking into account that the absolute value of the amplitude completely varies from individual to individual, it is impossible to avoid an influence of differences among individuals, which deteriorates accuracy of inference.    Patent Document 1: JP-A-2004-351184 (page 7 and FIG. 2)    Patent Document 2: JP-A-2001-141306 (page 10 and FIG. 1)    Patent Document 3: JP-A-7-299040    Patent Document 4: Japanese Patent No. 2816799    Patent Document 5: JP-A-2000-354683    Patent Document 6: JP-A-2003-227654    Patent Document 7: JP-A-2003-42509    Patent Document 8: Japanese Patent No. 2833082